The invention relates to the use of a fiber-reinforced plastic as a reinforcement system for a window or door frame hollow profile, which may particularly be embodied as a multi-chamber, extruded hollow profile comprising thermoplastic material.
Such a profile is known, among other things, from WO 01/06079, with both plastic as well as steel being mentioned as the material for the reinforcement system, embodied in the form of strip or bar-shaped reinforcement elements, with the steel variant being set apart by poorer heat insulation in reference to the plastic reinforcement. However, the heat insulation is of increasing importance in window construction. The reinforcement elements of WO 01/06079 may show punched recesses particularly at their opposite longitudinal edges, which enter into a form-fitting engagement with a frame profile.
Additionally, in DE 199 33 099 a plastic hollow-profile for windows or doors has become known in which the reinforcement system comprises metallic strips, which are connected to the plastic hollow profile in a form-fitting fashion via recesses. In order to produce these recesses the metallic strip must be locally punched, which requires additional production expenses.
If a window frame is to be produced from such profiles, the respective profile sections are sawed in a mitered fashion and welded to each other at the corner sections. When the profile is provided with reinforcements made from a metallic material, it must be ensured prior to welding that the reinforcement is recessed by a few millimeters at the ends of the plastic profile in order to not contact the welding hot-plate and thus preventing the feeding motion during the heating of the thermoplastic material. This is achieved in separately inserted reinforcement profiles such that an appropriately shortened profile is used. In reinforcement profiles, with the reinforcement embedded during the extrusion process, the reinforcement must be cut down by a few millimeters. Both measures aggravate the production of the frame.
The same problem arises when instead of a metallic reinforcement, the reinforcement is fiberglass-reinforced plastic profiles that are made from a thermoset material. The known fiberglass-reinforced PVC-profiles are of insufficient stability to withstand all stress potentially applied.